1. Field of the Invention
This invention relates to a catheter balloon for use in vasodilation. More particularly, it relates to a catheter balloon for vasodilation characterized by the fact that the balloon part of the vasodilating catheter balloon is provided with what concurrently serves as a lubricating portion and as a non-lubricating portion.
2. Description of the Prior Art
Generally, obvious signs of adhesion such as of blood clot, loose tissue, fragments from injured tissue, and products of extraneous reactions are observed frequently on the surfaces of substrates of medical tools and devices. For the purpose of minimizing these adverse phenomena, the practice of using materials of low friction for such substrates and the practice of coating the surfaces of such substrates with a hydrophilic polymer have been in vogue. Particularly, in the case of such medical tools as catheters which by nature are used as inserted in body cavities and blood vessels, since the alleviation of the resistance offered by the tools during the insertion thereof into body cavities results in preventing the tools from injuring the tissue and improving the operability of the tools, it is important to impart lubricity to the surfaces of such tools. For example, the practice of adopting substances of low friction like fluorine resin and polyethylene as materials for these medical tools and the practice of coating the surfaces of substrates with fluorine resin, silicone oil, olive oil, and glycerol are now prevailing. The method of coating, however, fails to provide lasting lubricity as desired, entails the problem of fallibility in respect that the applied coats of lubricating substances will easily depart, peel, or dissolve from the surfaces of substrates, and proves to be unbeneficial for medical tools.
JP-A-59-81,341 discloses a method for enabling the surface of a medical tool to manifest necessary lubricity by causing the unaltered isocyanate group on the surface to react with a hydrophilic polymer capable of forming a covalent bond with the isocyanate group. Since the hydrophilic polymer has N-vinyl-2-pyrrolidone as a main component thereof, for example, this method is at a disadvantage in respect that the lubricating layer to be formed thereby has too low strength to ensure manifestation of the lasting durability which is indispensable for repeated use of the coated medical tool. Thus, this method proves to be unbeneficial for medical tools. U.S. Pat. No. 4,100,309 has a disclosure to the effect that a copolymer of polyvinyl pyrrolidone with polyurethane is used as a substance possessing lubricity. The method taught by this invention indeed is satisfactory in terms of lubricity and lasting durability. When the copolymer is used on the surface of a balloon in the vasodilating catheter balloon which is one of medical tools, the coated balloon exhibits an excellent operability during the insertion thereof into a body cavity. When the coated balloon is inflated at a site selected for blockage in the blood vessel, however, the poor resistance of the surface of this balloon due to excessively high lubricity thereof often entails accidental slippage of the balloon from the target site (such as, for example, a site affected by stenosis) and renders the therapy difficult.
JP-B-1-33,181 discloses a method for imparting lubricity to the surface of a substrate forming a medical tool while the surface is in a state by causing a reactive functional group present in the surface to react with a maleic anhydride type polymeric material. Again this method is at a disadvantage in not ensuring safe retention of the treated substrate at the target site.
As described above, the conventional vasodilating catheter balloon possessing lubricity is handicapped by fallibility of retention of the balloon at the target site notwithstanding the excellent operability exhibited during the insertion thereof in a body cavity.
An object of this invention, therefore, is to provide a novel vasodilating catheter balloon.
Another object of this invention is to provide a vasodilating catheter balloon which is liberated from the various problems mentioned above and enabled to fulfill simultaneously high operability during the insertion into a body cavity and infallible retention of the balloon at the target site.